These proposed studies will investigate the factors which control renal hemodynamics and arterial blood pressure in both normotensive and hypertensive pregnancies. These proposed studies are divided into the following areas: 1). elucidation of the signal(s) causing and maintaining the gestational reduction in total peripheral and renal vascular resistance, and plasma and ECF expansion and characterization these events 2). vascular and glomerular reactivity to various vasopressor hormones throughout pregnancy; are exogenous and endogenous hormones seen differently? 3). investigation into sex differences in renal vasculature. 4). investigation of immediate and long term consequences to the kidney and cardiovascular system of the mother when pregnancy is superimposed on underlying hypertension; many different models will be employed. 5). investigation into the adverse interaction between reduction in uterine perfusion and pregnancy outcome. Studies will be performed using two in vivo experiment techniques; 1). the conscious chronically catheterized preparation which allows measurements to be made of renal and cardiovascular function, in completely unstressed conditions 2). the glomerular micropuncture technique which allows measurements to be made of segmental renal vascular resistances, pressures and flows. Also, a third, in vitro technique, using the isolated glomerulus will allow a direct assessment of glomerular reactivity to various vasoactive agents. Combination of these experimental tools will permit a thorough, and physiologically relevant investigation into the control of renal and cardiovascular function in normal and hypertensive pregnancies.